1. Field of the Invention
The present invention relates to an electrical switching apparatus and, more specifically, to a modular racking system for an electrical switching apparatus.
2. Background Information
An electrical switching apparatus, typically, includes a housing, at least one bus assembly having a pair of contacts, a trip device, and an operating mechanism. The housing assembly is structured to insulate and enclose the other components. The at least one pair of contacts include a fixed contact and a movable contact and typically include multiple pairs of fixed and movable contacts. Each contact is coupled to, and in electrical communication with, a conductive bus that is further coupled to, and in electrical communication with, an external line bus or a load bus. A trip device is structured to detect an over current condition and to actuate the operating mechanism. An operating mechanism is structured to both open the contacts, either manually or following actuation by the trip device, and close the contacts. That is, the operating mechanism includes both a closing assembly and an opening assembly, which may have common elements, that are structured to move the movable contact between a first, open position, wherein the contacts are separated, and a second, closed position, wherein the contacts are coupled and in electrical communication.
Typically, an electrical switching apparatus was either fixed in an enclosure or adapted to be a draw-out electrical switching apparatus. A fixed electrical switching apparatus was fixed to the line and load bus within the enclosure. A draw-out electrical switching apparatus included a disconnect or terminal on each conductive bus. Similarly, the line and load bus within the enclosure for a draw-out electrical switching apparatus each included a disconnect or terminal. Thus, as the draw-out electrical switching apparatus is being inserted into the enclosure, the draw-out electrical switching apparatus disconnects engage, and become in electrical communication with, the enclosure terminals. Conversely, when the draw-out electrical switching apparatus is moved out of the enclosure, the draw-out electrical switching apparatus disconnects disengage from the enclosure terminals.
Typically, the draw-out electrical switching apparatus includes a plurality of wheels structured to travel over a corresponding set of rails within the enclosure. In this configuration, the draw-out electrical switching apparatus disconnects and the enclosure disconnects are generally aligned. Further, a racking device is typically used to move the draw-out electrical switching apparatus into, and out of, the enclosure. The racking device includes an interlock actuator, discussed below, and a racking actuator. The racking actuator helps move the electrical switching apparatus over the rails and ensures that the disconnects fully engage each other during insertion and helps overcome frictional forces during removal.
As the enclosure line and load buses typically carry current when the electrical switching apparatus contacts are closed, it is very dangerous to move the draw-out electrical switching apparatus into, and out of, the enclosure with the contacts closed. Further, the operating mechanism closing assembly and opening assembly both utilize one or more springs to close and open the contacts. These springs, when charged, store mechanical energy. To ensure that the electrical switching apparatus contacts are not closed as the draw-out electrical switching apparatus is moved in or out of the enclosure, the draw-out electrical switching apparatus includes one or more interlock assemblies. Further, the electrical switching apparatus includes an interlock structured to release any stored mechanical energy within the opening or closing springs. An interlock assembly for the contacts engages the draw-out electrical switching apparatus operating mechanism and, when actuated, places the contacts in the first, open position. That is, if the contacts were in the second, closed position, the interlock assembly moves the contacts to, and maintains the contacts in, the first, open position, and, if the contacts were in the first, open position, the interlock assembly prevents the contacts from moving to the second, closed position. An interlock for the stored mechanical energy device also engages the draw-out electrical switching apparatus operating mechanism and, when actuated, releases the stored energy. The interlock assemblies are, typically, actuated by the racking device interlock actuator. The interlock assembly and the racking device interlock actuator are typically fixed to each other by one or more fasteners. Thus, any time the racking device is utilized, the interlock assembly should ensure that the springs are discharged, the contacts are open and the draw-out electrical switching apparatus may be safely moved.
Because a fixed electrical switching apparatus is not typically disconnected from the enclosure line and load buses, a fixed electrical switching apparatus does not include the racking device or a set of wheels structured to engage enclosure rails. Thus, manufacturers, typically, make two versions of an electrical switching apparatus; one that is structured to be a fixed electrical switching apparatus and one that is structured as a draw-out electrical switching apparatus. To reduce manufacturing costs, it would be advantageous to have a modular racking system that could be optionally added to an electrical switching apparatus. Further, customers may wish to adapt a fixed electrical switching apparatus to be a draw-out electrical switching apparatus, or vice-versa.
There is, therefore, a need for a modular racking system that may be removably coupled to an electrical switching apparatus.
There is a further need for a modular racking system wherein the modular racking system may be added to the electrical switching apparatus late in the manufacturing process or by a customer.